The present invention relates to a automotive headlamp in which a discharge bulb is used as a light source.
In the field of automotive headlamps, much recent attention has been paid to discharge bulbs in view of their good luminous efficiency and color properties as well as their long lifetime. Development activities directed to using discharge bulbs as automotive headlamps have been actively pursued.
A lighting circuit for applying a high voltage across the opposing electrodes of a discharge bulb is required for actuating the discharge bulb to start the discharge. As shown in FIG. 8 , a headlamp employing a discharge bulb has a structure in which a lighting circuit receiving casing 3 for housing a lighting circuit 4 therein is attached to the rear portion of a lamp body 1 in which a discharge bulb 2 is inserted. Various electronic components are mounted on a printed circuit board 5 within the lighting circuit 4.
In the prior art arrangement described above, however, the printed circuit board 5 is mounted in the casing 3 through screws or by bonding with an adhesive, so that the electronic components constituting the lighting circuit 4 are subject to vibration and the entry of moisture.